MINERAL SURFACE CONTROLS ON THE DIAGENETIC TRANSPORT OF OXALATE AND ALUMINUM

The importance of adsorption is virtually unknown at temperatures of > 25 degrees C. This study indicates that interactions between organic acids and mineral surfaces may control Al transport during elastic dia genesis. Oxalate adsorption onto alumina (gamma-Al2O3) was measured as a function of pH at 25 degrees and 60 degrees C in 0.1 M NaCl solutio ns. The thermodynamic stability of the surface Al-oxalate complex rema ins relatively constant with increasing temperature. Decreasing grain size amplifies the degree to which mineral surfaces control Al and oxa late concentrations through oxalate adsorption in fluid-rock systems. Therefore, diagenetic phase changes should be focused at discontinuiti es in mineral grain diameter. Furthermore, this grain size effect can influence aluminosilicate mineral solubilities and, therefore, may pla y an important role in determining the distribution and transport of A l and organic acid anions in sedimentary basins.